1. Field of the Invention
The present invention relates to an observation apparatus, and in particular to an observation apparatus for observing patterns such as circuits and characters formed in the surface or near the surface of semiconductor wafers and insulation substrates such as glass, ceramic and the like.
2. Description of the Prior Art
Up to now, during the manufacturing process of semiconductor integrated circuits, observation of patterns such as numbers, characters and circuits provided on the surface of semiconductor wafers (hereinafter referred to simply as xe2x80x9cwaferxe2x80x9d), liquid crystal substrates, glass, ceramic or resin have been carried out with an image detector such as a camera or the like. For example, during the manufacturing process, the identification code provided on a wafer is read, and then a predetermined process is carried out in accordance with such identification code.
In prior art observation devices, the amount of light received by an image detector (e.g., a camera) is adjusted by changing the emission intensity of the light source, and this is carried out by changing the current value or voltage value of the driving current of the light-emitting bodies.
Namely, in such prior art observation devices, a variable current driving circuit or a variable voltage driving circuit must be used for the driving circuit that drives the light-emitting portion. Consequently, the driving circuit of the light-emitting portion becomes relatively complex, and the overall size becomes larger as the number of light-emitting bodies capable of separate light emission is increased.
With a view toward overcoming the problems described above, it is an object of the present invention to provide an observation apparatus equipped with a simplified driving circuit for driving light-emitting bodies.
In order to achieve the object stated above, the observation apparatus of present invention is equipped with a light-emitting portion for shining light onto an observation object, image detection means for receiving light reflected from or passing through the observation object, light emission period establishing means for establishing a light emission period for the light-emitting portion, and light emission control means which activates the light-emitting portion to emit light synchronous with a vertical synchronizing signal of the image detection means, and which terminates the emission of light from the light-emitting portion after the established light emission period has elapsed.
Further, it is possible to use a horizontal synchronizing signal of the image detection means as a timing means to time the light emission period.